It has been known for many years that magnetic fields can influence biological processes. For example, in the article "Time-Varying Magnetic Fields: Effect on DNA Synthesis" Science 223:818-820 (1984), a correlation between DNA synthesis and time varying magnetic fields is shown. In the article "Effects of ELF (1-120 Hz) and Modulated (50 Hz) RF Fields on the Efflux of Calcium Ions From Brain Tissue In Vitro", Bioelectromagnetics 6:1-11 (1985), Blackman reports that calcium efflux from cerebral tissue can be increased by exposing the tissue to an electromagnetic field.
In addition, a number of devices and methodologies have been developed for the treatment of various medical conditions which rely on the application of specific magnetic fields to a biological subject or target tissue of a patient. For example, in U.S. Pat. No. 4,932,951 entitled "Method and Apparatus for Controlling Tissue Growth With an Applied Fluctuating Magnetic Field" the use of an applied magnetic field which combines with the existing geomagnetic field is described for regulating tissue growth. In U.S. Pat. No. 4,818,697, "Techniques for Enhancing the Permeability of Ions Through Membranes" and U.S. Pat. No. 5,059,298 entitled "Method and Apparatus for Regulating Transmembrane Ion Movement", there are described methods and apparatus for applying magnetic fields to biological systems based on achieving resonance states for ions such as calcium, magnesium and potassium. The specific resonances described therein are a function of the charge-to-mass ratios of the ions. The role of cyclotron resonance frequencies in transmembrane ion movement of selected ions through applied magnetic fields is also disclosed. In U.S. Pat. No. 5,087,336 entitled "Methods and Apparatus for Regulating Transmembrane Ion Movement Utilizing Selective Harmonic Frequencies and Simultaneous Multiple Ion Regulation", the interplay of harmonic frequencies and cyclotron resonance is also described.
Most recently research has been conducted on the question of whether there are health risks associated with electromagnetic fields produced from electric current-carrying devices such as power transmission lines, distribution lines, or even house wiring and grounding systems. Some researchers believe that a strong correlation exists between the incidence of certain diseases and the subject's proximity to sources of electromagnetic fields. For example, D. A. Savitz and E. E. Calle, in their study entitled "Leukemia and Occupational Exposure to Electromagnetic Fields: Review of Epidemiological Surveys", Journal of Occupational Medicine 29:47-51 (1987), present data suggesting an increased risk of leukemia among men with occupational exposure to 60 hertz (60 Hz) type electromagnetic fields. Additionally, R. S. Lynn, P. C. Dischinger, J. Conde, and K. P. Farrell have found that 60 Hz electromagnetic field exposure may promote brain tumors. These findings are presented in the article entitled "Electromagnetic Fields and the Occurrence of Brain Tumors: An Analysis of Possible Associations", Journal of Occupational Medicine 27:413-415 (1985). There are a number of theories which have been advanced in an effort to explain the apparent correlation between 60 Hz electromagnetic fields and perceived health risks and the issue is the subject of much debate.
It is also known that a number of portable devices are available which sense magnetic fields and which provide a readout of the field parameters. None of these prior art devices, however, provide a portable device which determines the magnitudes and directions of dc with respect to a known direction such as due north (including the geomagnetic field) and ac magnetic fields along three perpendicular axes, calculates specific field values which are automatically compared to a second set of values representative of ion resonance values and displays information regarding the presence of a field value near a resonant value which could pose health risks. The present invention addresses this need.